Abnormality diagnostic apparatus for gas sensor

Abstract

An abnormality diagnostic apparatus for a gas sensor includes a NOx sensor includes a main pump cell, an auxiliary pump cell, and a detection cell. The apparatus diagnoses at least one of the detection cell, the main pump cell, and the auxiliary pump cell for an abnormality, based on at least one of a rising characteristic of a NOx output of the detection cell immediately after a start of detection of the NOx output, its peak value, and its subsequent falling characteristic. An abnormality of the detection cell is determined if a speed with which the NOx output rises is small; an abnormality of at least one of the main pump cell and the auxiliary pump cell is determined if a speed with which the NOx output falls is small; and an abnormality of the detection cell is determined if the peak value of the NOx output is small.

1 - 9 . (canceled) 
     
     
         10 . An abnormality diagnostic apparatus for a gas sensor, the gas sensor including: a main pump cell for pumping oxygen out of a gas to be measured; an auxiliary pump cell for pumping oxygen further out of the gas to be measured; and a detection cell for detecting concentration of a specific gas component contained in the gas to be measured out of which oxygen has been pumped by the main pump cell and the auxiliary pump cell, the abnormality diagnostic apparatus comprising:
 abnormality diagnosis means for diagnosing an abnormality in at least one of the detection cell, the main pump cell, and the auxiliary pump cell based on at least one of a rising characteristic of a cell output of the detection cell immediately following a start of detection of the cell output, a peak value thereof, and a subsequent falling characteristic thereof, during warming of the gas sensor, wherein   if a peak value after rising of the cell output is smaller than a predetermined threshold value, the abnormality diagnosis means determines that an abnormality has occurred in the detection cell.   
     
     
         11 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , wherein
 if a speed with which the cell output rises is smaller than a predetermined threshold value, the abnormality diagnosis means determines that an abnormality has occurred in the detection cell.   
     
     
         12 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , wherein
 if a speed with which the cell output falls after rising is smaller than a predetermined threshold value, the abnormality diagnosis means determines that an abnormality has occurred in at least one of the main pump cell and the auxiliary pump cell.   
     
     
         13 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , wherein
 the abnormality diagnosis means determines whether there is an abnormality of being out of a range of the gas sensor.   
     
     
         14 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , wherein
 the abnormality diagnosis means determines whether there is an abnormality of reduced response of the gas sensor.   
     
     
         15 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , wherein
 the abnormality diagnosis means determines whether there is an abnormality arising from an open circuit of the gas sensor.   
     
     
         16 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , wherein
 the abnormality diagnosis means determines whether there is an abnormality arising from a short circuit of the gas sensor.   
     
     
         17 . The abnormality diagnostic apparatus for the gas sensor according to  claim 10 , further comprising:
 second abnormality diagnosis means for determining that an abnormality has occurred in the auxiliary pump cell, if a difference between an output of the main pump cell and an output of the auxiliary pump cell is greater than a predetermined threshold value.   
     
     
         18 . An abnormality diagnostic apparatus for a gas sensor, the gas sensor including: a main pump cell for pumping oxygen out of a gas to be measured; an auxiliary pump cell for pumping oxygen further out of the gas to be measured; and a detection cell for detecting concentration of a specific gas component contained in the gas to be measured out of which oxygen has been pumped by the main pump cell and the auxiliary pump cell, the abnormality diagnostic apparatus comprising:
 abnormality diagnosis device for diagnosing an abnormality in at least one of the detection cell, the main pump cell, and the auxiliary pump cell based on at least one of a rising characteristic of a cell output of the detection cell immediately following a start of detection of the cell output, a peak value thereof, and a subsequent falling characteristic thereof, during warming of the gas sensor, wherein   if a peak value after rising of the cell output is smaller than a predetermined threshold value, the abnormality diagnosis device determines that an abnormality has occurred in the detection cell.